1. Field of the Invention
The present invention relates to the transfer and stacking of sheet material and especially to the transfer of preglued loose assemblies of wood veneer to a stacking station and the stacking of such assemblies for pressing into plywood.
2. Description of the Prior Art
The closest known prior apparatus for transferring and stacking veneer sheet assemblies preparatory to pressing the assemblies into plywood sheets is shown in U.S. Pat. No. 3,446,368. Although such prior apparatus is capable of transferring and stacking sheet assemblies, it is a complex and costly machine. The arms for transferring the sheet material to the stacking apparatus undergo four separate rectilinear movements for which appropriate mechanism must be provided to accomplish, including (1) an elevating movement to lift sheet material from conveyor belts, (2) an extending movement to transfer sheet material to a stacking station, (3) a lowering movement while extended to position the sheet in closely overlying relationship to a load-receiving device of a stacking apparatus, and finally (4) a retracting movement to return the arms to their original positions below the level of the aforementioned conveyor belts.
In addition, such prior apparatus has an accumulator arm mechanism built into the same frame that supports the transfer arm and conveyor belt assembly, thereby further increasing the cost and complexity of the apparatus and decreasing its versatility. Because a single supporting frame is burdened with all of the aforementioned mechanisms, there is insufficient space to enable the passage of a stack of sheet assemblies in a direction beneath such frame on a suitable transfer conveyor. Therefore, a completed stack must be removed from the stacking station either in the opposite direction or in directions normal to the alignment of the conveyor and stacking frames, thereby eliminating a space-saving option in the layout of a plywood layup line for optimum space utilization within a plywood mill.
A further disadvantage of the prior mentioned apparatus is that because of its peculiarities of construction it cannot be readily converted from a right-hand side shift to a left-hand side shift machine, or vice versa, without extensive modification. This necessitates knowledge of how the machine will be used in a plywood mill, i.e. as a left-hand or right-hand shift machine, before the machine is built.
Accordingly, there is a need for an improved apparatus for transferring and stacking assemblies of veneer in the manufacture of plywood.